CO2 simulation

This page contains information about the carbon dioxide (CO₂) simulation in GEOS-Chem.

Overview

The original GEOS-Chem CO₂ simulation was developed by Parv Suntharalingam (Suntharalingam et al., 2003; 2004), now at the University of East Anglia. A major update to the CO₂ simulation was completed in 2010 by Ray Nassar and Dylan B.A. Jones of the University of Toronto (Nassar et al., 2010). The latest update to the CO₂ simulation was developed by Ray Nassar (now at Environment Canada) and appears in GEOS-Chem v10-01, which was released on 2015 May 1.

v8-03-02 update (April 2010)

The 2010 update retained the original six CO₂ fluxes: fossil fuel, ocean exchange, biomass burning, biofuel burning, balanced terrestrial exchange (CASA) and net annual terrestrial exchange. Other inventories are available as options for some of these fluxes and other new fluxes were added such as CO₂ emissions from international shipping and aviation. There is also an optional feature to include CO₂ production from the oxidation of CO, CH₄ and NMVOCs. This chemical source concept was first highlighted by Enting and Mansbridge (1991). Although a few attempts have been made by other groups in the past, this implementation made GEOS-Chem the only 3-D global model to account for the chemical production of CO₂. The GEOS-Chem implementation uses an approach similar to that described in Suntharalingam et al. (2005), with some updated year-specific numbers and some other modifications described in Nassar et al. (2010). The full GEOS-Chem CO₂ update was applied to and tested with v8-02-01 (along with some patches). It has been publicly available in GEOS-Chem release v8-03-02 and later versions, along with an update to the GEOS-Chem online manual. The references below are cited in the updated code's comments and online manual, and include the new CO₂ simulation description paper Nassar et al. (2010).

v10-01 update (May 2015)

GEOS-Chem v10-01 includes a substantial update to the CO₂ simulation. A number of new or updated inventories have now been added at the same time as emissions are now handled by HEMCO. HEMCO reads emissions from netCDF files at any specified resolution and regrids the data, along with applying scaling factors where applicable. Major changes in this update include new options for fossil fuel emissions, biospheric fluxes and ocean fluxes and a modified treatment of the chemical source surface correction.

The CO₂ emission updates are the following:

1) Carbon Dioxide Information Analysis Center (CDIAC) gridded data has been updated to include additional years [Andres et al. 2011] – CDIAC v2014 now extends to 2011 and RN has applied BP scaling for 2012 and 2013 with a projection for 2014 based on the Global Carbon Project values.

2) Open-source Data Inventory for Atmospheric CO₂ emissions (ODIAC version 2013) fossil fuel option is now added [Oda and Maksyutov, 2011], which is known to have a more reliable spatial distribution for large countries but is consistent with an earlier version of CDIAC version for national emission totals.

3) Temporal Improvements for Monitoring Emissions by Scaling (TIMES) is now added [Nassar et al., 2013], which introduces weekly and diurnal variations to national fossil fuel emissions

4) The Takahashi et al. (2009) ocean fluxes in the model were included as a 1-year climatology corresponding to the year 2000 with a sink of 1.4 PgC. The same paper also describes a method for scaling the Takahashi et al. (2009) fluxes with year-specific atmospheric CO₂ to yield year specific fluxes with an increasing global sink. This approach has been applied to scale the fluxes for 2000-2013 inclusive with an ocean sink ranging from (1.4 to 2.6 PgC/yr).

5) Balanced biospheric CO₂ uptake and emission from the Simple Biospheric Model version 3 (SiB3) for the years 2006-2010 from Nick Parazoo [Messerschmidt et al. 2012]

6) Aviation emissions spatial and temporal distributions now come from AEIC. Updates to the scaling factors for the global annual emission amount from the International Energy Agency [Olsen et al., 2013] are now used for 1990-2008. A new system for aviation surface correction factors is now implemented which scales national fossil fuel emissions by a factor slightly less than 1 in order to remove the estimated contribution from domestic aviation emission, which is counted in the air instead of at the surface.

7) The chemical source of CO₂ now spans a larger time period 2000-2009. The 2008 chemical source was recalculated with GFED for 2008, which was unavailable at the time of the previous update. A 2009 chemical source is now added. The surface correction approach has been revised such that the magnitude of the fossil fuel surface correction is now year specific for 1980-2014. In v8-03-02, the percentage of fossil fuel carbon emissions released as CO (and other carbon species like CH₄ and non-methane hydrocarbons) was assumed to be 4.89% based on the work of Suntharalingam et al. [2005], with no temporal dependence. However, studies have demonstrated that even as fossil fuel CO₂ emissions have continually risen for decades, fossil fuel CO emissions have held essentially constant since about 1980 at 500-600 Tg CO/year [Granier et al., 2011]. Fossil fuel CH₄ is also found to be roughly constant at 80 TgCH₄/yr in CarbonTracker-CH₄. In GEOS-Chem v10-01, the fossil fuel emission surface correction for the chemical source from Nassar et al. [2010] has been modified based on the decreasing CO/CO₂ and CH4/CO₂ emission ratios, attributed to improved technology in both developed and developing countries, demonstrated by roughly constant CO and CH₄ emissions despite increasing CO₂ emissions. The surface correction goes from 5.28% in 1980 and decreases to 2.84% in 2013, replacing the constant value of 4.89% prior to v10-01. This new approach assumes a negligible percentage of fossil fuel carbon from sources other than CO₂, CO, and CH₄ (such as non-methane hydrocarbons) and assumes that the combustion completeness is globally-uniform. The assumption of global uniformity, though not a good assumption for the past, is becoming more reasonable as the developed countries adopt cleaner combustion technology releasing less non-CO₂ carbon species. Note that for the 3D emission sources, both aviation CO₂ emissions and CO₂ chemical production, there has been a change in emission units to molecules/cm²/s instead of molecules/cm³/s, for consistency with HEMCO implementation in other parts of GEOS-Chem.

Note: The new HEMCO netCDF file for CDIAC national fossil fuel CO₂ emissions is not ready due to a delay from CDIAC, but is expected to be available by mid-May.

Note: Nassar et al. (2010) remains the recommended reference for the GEOS-Chem CO₂ simulation from v8-03-02 to the present version.

References

1. Andres. R.J., J.S Gregg, L. Losey, G. Marland, T.A. Boden (2011), Monthly, global emissions of carbon dioxide from fossil fuel consumption, Tellus 63B, 309-327.
2. Granier, C., et al. (2011), Evolution of anthropogenic and biomass burning emissions of air pollutants at global and regional scales during the 1980-2010 period, Climatic Change, 109:163-190, doi:10.1007/s10584-011-0154-1.
3. Keller, C.A., M.S. Long, R.M. Yantosca, A.M. DaSilva, S. Pawson, D.J. Jacob (2014), HEMCO v1.0: a versatile, ESMF-compliant component for calculating emissions in atmospheric models, Geosci., Model Dev., 7, 1409–1417, doi:10.5194/gmd-7-1409-2014.
4. Messerschmidt, J., N. Parazoo, N.M. Deutscher, C. Roehl, T. Warneke, P.O. Wennberg, and D. Wunch (2012), Evaluation of atmosphere-biosphere exchange estimations with TCCON measurements, Atmos. Chem. Phys. Discussions, 12, 12759-12800, doi:10.5194/acpd-12-12759-2012.
5. Nassar, R., D.B.A. Jones, P. Suntharalingam, J.M. Chen, R.J. Andres, K.J. Wecht, R.M. Yantosca, S.S. Kulawik, K.W. Bowman, J.R. Worden, T. Machida and H. Matsueda (2010), Modeling global atmospheric CO₂ with improved emission inventories and CO₂ production from the oxidation of other carbon species, Geoscientific Model Development, 3, 689-716.
6. Nassar, R., L. Napier-Linton, K.R. Gurney, R.J. Andres, T. Oda, F.R. Vogel, F. Deng (2013), Improving the temporal and spatial distribution of CO₂ emissions from global fossil fuel emission datasets, Journal of Geophysical Research: Atmospheres, 118, 917-933, doi:10.1029/2012JD018196.
7. Oda, T. and S. Maksyutov (2011), A very high-resolution (1 km x 1 km) global fossil fuel CO₂ emission inventory derived using a point source database and satellite observations of nighttime lights, Atmos. Chem. Phys., 11, 543–556, doi:10.5194/acp-11-543-2011.
8. Olsen, S.C., D.J. Weubbles, B. Owen (2013), Comparison of global 3-D aviation datasets, Atmos. Chem. Phys., 13, 429–441, doi:10.5194/acp-13-429-2013.
9. Simone, N., M. Stettler, S. Eastham, S. Barrett, Aviation Emissions Inventory Code (AEIC) User Manual (R1), Laboratory for Aviation and the Environment, Massachusetts Institute of Technology, January 2013, Report No: LAE-2013-001-N, www.LAE.MIT.edu.
10. Takahashi, T., Sutherland, S. C., Wanninkhof, R., Sweeney, C., Feely, R. A., Chipman, D. W., Hales, B., Friederich, G., Chavez, F., Sabine, C., Watson, A., Bakker, D. C. E., Schuster, U., Metzl, N., Yoshikawa-Inoue, H., Ishii, M., Midorikawa, T., Nojiri, Y., K¨ortzinger, A., Steinhoff, T., Hoppema, M., Olafsson, J., Arnarson, T. S., Tilbrook, B., Johannessen, T., Olsen, A., Bellerby, R., Wong, C. S., Delille, B., Bates, N. R., and de Baar, H. J. W (2009), Climatological mean and decadal change in surface ocean pCO2, and net sea-air CO₂ flux over the global oceans, Deep-Sea Res. II, 56(8–10), 554–577, doi:10.1016/j.dsr2.2008.12.009.

--Ray Nassar, 2015 May 12

Additional Update and Bug Fix

These updates were included in the 1-month benchmark simulation v11-01c and approved on 14 Sept 2015.

1) The new HEMCO netCDF file for CDIAC national fossil fuel CO₂ emissions is now available (as of September 4, 2015). The file contains data for 1980-2014. For 1980-2011 the data come directly from the Carbon Dioxide Information Analysis Center (CDIAC) 1x1 gridded dataset (Andres et al., 2011) version 2014. For 2012-2014, the CDIAC year 2011 spatial and seasonal distribution has been scaled using the BP Statistical Review of World Energy 2015. The ratio of emissions from each year (2012-2014) against 2011 emissions for the 20 highest CO₂ emitting countries and for the remainder of the world from the BP data, were used to scale the spatial-temporal CDIAC distributions for 2011. Note: there are differences in the component CO₂ emissions in the CDIAC and BP methodologies, but this should not be a major factor such that this approach is considered better than the simple alternative approach of simply using 2011 for subsequent years.

2) A new file is now available for CASA balanced biosphere fluxes. This file has been reprocessed to replace an error in the earlier available version, which was based on CASA bpch files from back in 2005. For some reason, the file for day of year 189 was renamed to “nep.geos.2x25.189.orig” and the file for day 188 was copied and renamed to “nep.geos.2x25.189” so there was a resulting anomaly in the date-times in the netCDF file since actual date-times for day 189 were missing, and day 188 appeared twice. This has now been corrected using day 189.orig to create a new netCDF file so that there are no oddities with dates in the file.

--Ray Nassar, 2015 September 4

Authors and collaborators

• Ray Nassar (Environment Canada)

CO₂ simulation user groups

User Group	Personnel	Projects
University of Toronto	Dylan Jones	Model updates and application to inverse modeling
Korea Environment Institute (KEI)	Changsub Shim
University of Colorado Boulder	Daven Henze	CO2 adjoint
UEA	Chen	Inverse modeling of CO2 using satellite
Tsinghua University	Yuxuan Wang ; Mingwei Li
Environment Canada	Ray Nassar	CO2 modeling and source sink estimation using satellite and in situ data
Caltech		CO2 source/sink estimation using ground-based FTS data
University of Wollongong	Nicholas Deutscher	CO2 source/sink estimation using ground-based FTS (TCCON) data and co-located surface measurements. Focus on Australia
Add yours here!

Validation

In Nassar et al. (2010) model comparisons are made with GLOBALVEIW-CO2 (http://www.esrl.noaa.gov/gmd/ccgg/globalview/co2/co2_intro.html) and CONTRAIL (Comprehensive Observation Network for TRace gases by AIrLiner) measurements. In other work, the CO₂ simulation has also been compared with aircraft observations from the HIAPER Pole-to-Pole Observations (HIPPO) campaigns of 2009 (Wofsy et al., 2010).

Restart Files

Description

In GEOS-Chem v10-01 and higher versions, you can create run directories for the CO2 simulation from the GEOS-Chem Unit Tester package. The information below is therefore obsolete, but we will leave it here for reference.

Some single-tracer restart files are available:

restart.20000101

CO2 restart file for GEOS4 (30 levels) on date 2000-01-01

restart.20040101

CO2 restart file for GEOS5 (47 levels) on date 2004-01-01

These two restart file have uniform CO₂ values of 367.2 ppm for 2000-01-01 and 375.0 ppm for 2004-01-01, which are reasonable estimates of the global mean, but not realistic in the global distribution. Spinning up for one year will result in a realistic distribution in terms of both the global mean value and gross features (latitudinal gradient and seasonal/diurnal cycle) but accurate work will require adjusting or calibrating the restart file with actual measurements for the start of your run. The method of calibration using the sparse in situ measurements and/or satellite observations can be an active area of research on its own, so determining the approach to this is left to the user.

Downloading

In GEOS-Chem v10-01 and higher versions, you can create run directories for the CO2 simulation from the GEOS-Chem Unit Tester package. The information below is therefore obsolete, but we will leave it here for reference.

You can use the Git version control software to download GEOS-Chem run directories containing the above-mentioned restart files and other relevant input files (e.g. input.geos).

To download the GEOS-4 (30 levels) run directory, use this command:

git clone git://git.as.harvard.edu/bmy/GEOS-Chem-rundirs/2x2.5/geos4/CO2_run

To download the GEOS-5 (47 levels) run directory, use this command:

git clone git://git.as.harvard.edu/bmy/GEOS-Chem-rundirs/2x2.5/geos5/CO2_run

Nested-grid CO2 simulation

This update was tested in the 1-month benchmark simulation v9-01-03h and approved on 09 Mar 2012.

Yuxuan Wang wrote:

The nested-grid CO2 simulation is developed and tested based on v8-02-01. Except for code changes for nested-grid simulation in general, specific changes are made to read the CO2 fluxes at 0.5x0.667 resolution . These fluxes are regridded to 0.5x0.667 either from 1x1 input files on the fly when running GEOS-Chem or from 2x2.5 data files off-line using IDL.

--Melissa Payer 16:00, 2 December 2011 (EST)

References

1. Andres, R. J., G. Marland, I. Fung, and E. Matthews, A 1°x1° distribution of carbon dioxide emissions from fossil fuel consumption and cement manufacture, Global Biogeochem. Cycles, 10, 419–429, 1996.
2. Andres, R. J., Gregg, J. S., Losey, L., Marland, G., and Boden, T. A.: Monthly, global emissions of carbon dioxide from fossil fuel consumption, Tellus B, 63B, 2011.
3. Baker, D. F., et al., TransCom 3 inversion intercomparison: Impact of transport model errors on the interannual variability of regional CO₂ fluxes, 1988-2003, Global Biogeochem. Cycles, 20, GB1002, doi:10.1029/2004GB002439, 2006.
4. Boden, T.A., G. Marland, and R.J. Andres, Global, Regional, and National Fossil-Fuel CO₂ Emissions. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. doi 10.3334/CDIAC/00001, 2009.
5. Corbett & Koehler, Updated emissions from ocean shipping, J. Geophys. Res., 108, D20, 4650, 2003.
6. Corbett, J. J., and H. W. Koehler, Considering alternative input parameters in an activity-based ship fuel consumption and emissions model: Reply to comment by Øyvind Endresen et al. on Updated emissions from ocean shipping, J. Geophys. Res., 109, 2004.
7. Duncan, B. N., R. V. Martin, A. C. Staudt, R. Yevich, and J. A. Logan, Interannual and seasonal variability of biomass burning emissions constrained by satellite observations, J. Geophys. Res., 108(D2), 4100, doi:10.1029/2002JD002378, 2003.
8. Endresen, O, et al., A historical reconstruction of ships fuel consumption and emissions, J. Geophys. Res, 112, D12301, 2007.
9. Enting, I. G. and Mansbridge, J. V.: Latitudinal distribution of sources and sinks of CO₂: results of and inversion study, Tellus B, 43, 156–170, 1991.
10. Kim, B. Y., et al., System for assessing Aviation's Global Emissions (SAGE) Version 1.5 global Aviation Emissions Inventories for 2000-2004, 2005.
11. Kim, B. Y., et al., System for assessing Aviation’s Global Emissions (SAGE), Part 1: Model description and inventory results, Transportation Research, Part D 12, 325–346, 2007.
12. Le Quere, C. et al., Trends in the sources and sinks of carbon dioxide, Nature Geoscience, doi:10.1038/ngeo689, 2009.
13. Nassar, R., D. B. A. Jones, P. Suntharalingam, J. M. Chen, R. J. Andres, K. J. Wecht, R. M. Yantosca, S. S. Kualwik, K. W. Bowman, J. R. Worden, T. Machida, H. Matsueda, Modeling global atmospheric CO₂ with improved emission inventories and CO₂ production from the oxidation of other carbon species, Geoscientific Model Development, 3, 689-716, 2010.
14. Olsen, S. C., and J. T. Randerson, Differences between surface and column atmospheric CO₂ and implications for carbon cycle research, J. Geophys. Res., 109, D02301, doi:10.1029/2003JD003968, 2004.
15. Potter, C. S., J. T. Randerson, C. B. Field, P. A. Matson, P. M. Vitousek, H. A. Mooney, and S. A. Klooster, Terrestrial ecosystem production: A process model based on global satellite and surface data, Global Biogeochem. Cycles, 7, 811–841, 1993.
16. Sausen, R. and U. Schumann, Estimates of the Climate Response to Aircraft CO₂ and NO_x Emissions Scenarios, Climate Change, 44: 27-58, 2000.
17. Suntharalingam, P., C. M. Spivakovsky, J. A. Logan, and M. B. McElroy, Estimating the distribution of terrestrial CO₂ sources and sinks from atmospheric measurements: Sensitivity to configuration of the observation network, J. Geophys. Res., 108(D15), 4452, doi:10.1029/2002JD002207, 2003.
18. Suntharalingam, P., D. J. Jacob, P. I. Palmer, J. A. Logan, R. M. Yantosca, Y. Xiao, M. J. Evans, D. G. Streets, S. L. Vay, and G. W. Sachse, Improved quantification of Chinese carbon fluxes using CO₂/CO correlations in Asian outflow, J. Geophys. Res., 109, D18S18, doi:10.1029/2003JD004362, 2004.
19. Suntharalingam, P., J. T. Randerson, N. Krakauer, J. A. Logan, and D. J. Jacob, Influence of reduced carbon emissions and oxidation on the distribution of atmospheric CO₂: Implications for inversion analyses, Global Biogeochem. Cycles, 19, GB4003, doi:10.1029/2005GB002466, 2005.
20. Takahashi, T., R. A. Feely, R. Weiss, R. H. Wanninkhof, D. W. Chipman, S. C. Sutherland, T. T. Takahashi, Global air-sea flux of CO₂: an estimate based on measurements of sea-air pCO₂ difference, Proc. Natl. Acad. Sci., 94, 8292–8299, 1997.
21. Takahashi, T., et al., Climatological mean and decadal change in surface ocean pCO₂, and net sea–air CO₂ flux over the global oceans, Deep-Sea Res. II, doi:10.1016/j.dsr2.2008.12.009, 2009.
22. Wang, C., J.J. Corbett, J. Firestone, Modeling Energy Use and Emissions from North American Shipping: Application of the Ship Traffic, Energy, and Environment Model, Environ. Sci. Technol., 41, 3226-3232, 2008.
23. Wilkersen, J.T. et al., Analysis of emission data from global commercial Aviation: 2004 and 2006, Atmos. Chem. Phys. Disc., 10, 2945-2983, 2010.
24. Wofsy, S.C., et al., HIAPER Pole-to-Pole Observations (HIPPO): Fine grained, global scale measurements of climatically important atmospheric gases and aerosols, Proceedings of the Royal Society A, 369, 2073-2086, 2011.
25. Yevich, R., and J. A. Logan, An assessment of biofuel use and burning of agricultural waste in the developing world, Global Biogeochem. Cycles, 17(4), 1095, doi:10.1029/2002GB001952, 2003. PDF

Previous issues that are now resolved

Monthly CDIAC CO2 emissions

In GEOS-Chem v10-01 and higher versions, CO2 emissions data is read from netCDF files by the HEMCO emissions component. Please see our HEMCO data directories wiki page for more information about the latest CO2 emissions inventories.

Although GEOS-Chem v8-03-02 will be released with the functionality to run with monthly fossil fuel CO₂ emissions from CDIAC (R.J. Andres), the inventory files most likely will not be released until a later date, when the submitted paper Andres et al. (2010) is at a sufficient stage. Until then, annually-averaged fossil fuel CO₂ emissions must be selected in the input.geos file.

--Bob Y. 12:26, 29 March 2010 (EDT)

--Ray Nassar 9:48, 25 June 2010 (EDT)

Update: 25 Feb 2010: Updated annual and monthly fossil fuel CO2 emissions from CDIAC (version 2010 by R. Andres) are now available for use in GEOS-Chem v8-03-02 and higher versions. These data are located in the data directories:

GEOS_2x2.5/CO2_201003/fossilfuel_andres/annual_v2010
GEOS_2x2.5/CO2_201003/fossilfuel_andres/monthly_v2010

GEOS_4x5/CO2_201003/fossilfuel_andres/annual_v2010
GEOS_4x5/CO2_201003/fossilfuel_andres/monthly_v2010

The 1° x 1° data will be available by special request. Please contact the GEOS-Chem Support Team.

For more information, please see the following README files:

1. 2° x 2.5° global data: GEOS_2x2.5/CO2_201003/fossilfuel_andres/README
2. 4° x 5° global data: GEOS_2x2.5/CO2_201003/fossilfuel_andres/README

--Bob Y. 11:48, 25 February 2011 (EST)

Fix for regridding error in offline CO2 simulation

We have corrected this issue as a post-release patch on 22 Sep 2012. This issue does not affect the full-chemistry simulations, only the CO2 simulation.

In GEOS-Chem v10-01 and higher versions, CO2 emissions data is read from netCDF files by the HEMCO emissions component. Please see our HEMCO data directories wiki page for more information about the latest CO2 emissions inventories. The code listed below is therefore obsolete and has been removed from GEOS-Chem.

Ray Nassar wrote:

There is a bug in v9-01-03 for the CO2 simulation that causes a crash. It relates to the MAP_A2A regridding and the fact that the net terrestrial exchange file is named with geos.1x1 (360x181) although it is actually generic 1x1 (360x180) and it is trying to be read as geos.1x1.

Bob Yantosca wrote:

I fixed the issue in the CO2 code. To avoid further confusion, I made a symbolic link in the data directory:

   cd /as/data/geos/GEOS_1x1/CO_201003
   ln –s Net_terrestrial_exch_5.29Pg.geos.1x1 Net_terrestrial_exch_5.29Pg.generic.1x1

and then I made these changes in the code:

         ! Arrays and pointers
         REAL*4                 :: ARRAY    (IIPAR,JJPAR,1)
         REAL*4                 :: ARRAY_1x1(I1x1,J1x1-1,1)
         REAL*8,  TARGET        :: GEN_1x1  (I1x1,J1x1-1,1)
         REAL*8,  TARGET        :: GEOS_GRID(IIPAR,JJPAR,1)
         REAL*8,  POINTER       :: INGRID (:,:) => NULL()
         REAL*8,  POINTER       :: OUTGRID(:,:) => NULL()

         . . .
 
         !------------------------------------
         ! Read climatological Bionet data
         !------------------------------------       
         IF ( LBIONETCLIM ) THEN

            ! TAU value for start of "generic" year 2000
            TAU = GET_TAU0( 1, 1, 2000 )
   
   !-----------------------------------------------------------------------------
   !%%% v9-01-03 POST-RELEASE PATCH (bmy, 10/2/12)
   !%%% NOTE: Someone mislabeled the Net_terrestrial_exch file, it is labeled
   !%%% "geos.1x1" but is on the GENERIC 1x1 grid.  Therefore, we shall rename
   !%%% this file accordingly and use the generic grid indices (I1x1,J1x1-1)
   !%%% etc. below. (bmy, 10/2/12)
   !%%%         ! Filename
   !%%%         FILENAME = TRIM( DATA_DIR_1x1 )  //  
   !%%%     &              'CO2_201003/Net_terrestrial_exch_5.29Pg.geos.1x1'
   !%%% 
   !%%%         ! Echo info
   !%%%         WRITE( 6, 100 ) TRIM( FILENAME )
   !%%%
   !%%%         ! Read Net Terrestrial CO2 Exchange [molec/cm2/s]
   !%%%         CALL READ_BPCH2( FILENAME, 'CO2-SRCE', 6, 
   !%%%     &                    TAU,       I1x1,      J1x1      
   !%%%     &                    1,         ARRAY,     QUIET=.TRUE. )
   !%%%
   !%%%         ! Cast to REAL*8 before regridding
   !%%%         GEOS_1x1(:,:,1) = ARRAY(:,:,1)
   !%%%
   !%%%         ! File with lat/lon edges for regridding
   !%%%         LLFILENAME = TRIM( DATA_DIR_1x1) //
   !%%%     &                'MAP_A2A_Regrid_201203/MAP_A2A_latlon_geos1x1.nc'
   !%%%
   !%%%         ! Regrid from GEOS 1x1 --> current model resolution
   !%%%         INGRID  => GEOS_1x1 (:,:,1)
   !%%%         OUTGRID => GEOS_GRID(:,:,1)
   !%%%         CALL DO_REGRID_A2A( LLFILENAME, I1x1,    J1x1, 
   !%%%     &                       INGRID,     OUTGRID, PERAREA=0,
   !%%%     &                       netCDF=.TRUE.                   )
   !-----------------------------------------------------------------------------
                 
            ! Filename
            FILENAME = TRIM( DATA_DIR_1x1 )                      //  
        &              'CO2_201003/'                             //
        &              'Net_terrestrial_exch_5.29Pg.generic.1x1'
     
            ! Echo info
            WRITE( 6, 100 ) TRIM( FILENAME )

            ! Read Net Terrestrial CO2 Exchange [molec/cm2/s]
            CALL READ_BPCH2( FILENAME, 'CO2-SRCE', 6, 
        &                    TAU,       I1x1,      J1x1-1,
        &                    1,         ARRAY_1x1, QUIET=.TRUE. )

            ! Cast to REAL*8 before regridding
            GEN_1x1(:,:,1) = ARRAY_1x1(:,:,1)

            ! File with lat/lon edges for regridding
            LLFILENAME = TRIM( DATA_DIR_1x1)            //
        &                'MAP_A2A_Regrid_201203/'       //
        &                'MAP_A2A_latlon_generic1x1.nc'

            ! Regrid from GEOS 1x1 --> current model resolution
            INGRID  => GEN_1x1  (:,:,1)
            OUTGRID => GEOS_GRID(:,:,1)
            CALL DO_REGRID_A2A( LLFILENAME, I1x1,    J1x1-1, 
        &                       INGRID,     OUTGRID, PERAREA=0,
        &                       netCDF=.TRUE.                   )

        ! Free pointers
        NULLIFY( INGRID, OUTGRID )
        
        ... etc ...    

I pushed these to the GEOS_Chem repository (and also the GC_Bleeding_Edge repository). You can get it with:

    git pull git://git.as.harvard.edu/bmy/GEOS-Chem master

The commit was tagged with “Fix_for_CO2_sim” and is labeled:

   v9-01-03 post-release patch to fix bug in CO2 simulation

--Bob Y. 15:20, 20 December 2012 (EST)